https://bashny.net/Isida/2012/10/21/vidimoe-ne-vsegda-yavlyaetsya-tem-chem-nam-kazhetsya-vam-kazhetsya-chto-verhnyaya-polovina-temnee-nizhney-zakroyte-palcem-soedinitelnuyu-liniyu-mezhdu-nimi.html